Publications

Private Database Queries Using Somewhat Homomorphic Encryption

Abstract:
In a private database query system, a client issues queries to a database and
obtains the results without learning anything else about the database and
without the server learning the query. While previous work has yielded systems
that can efficiently support disjunction queries, performing conjunction
queries privately remains an open problem. In this work, we show that using a
polynomial encoding of the database enables efficient implementations of
conjunction queries using somewhat homomorphic encryption. We describe a
three-party protocol that supports efficient evaluation of conjunction
queries. Then, we present two implementations of our protocol using Paillier's
additively homomorphic system as well as Brakerski's somewhat homomorphic
cryptosystem. Finally, we show that the additional homomorphic properties of
the Brakerski cryptosystem allow us to handle queries involving several
thousand elements over a million-record database in just a few minutes, far
outperforming the implementation using the additively homomorphic system.